Winnebago County was formed on January 16, 1836 out of Jo Daviess and LaSalle counties. It was named for the Winnebago Tribe of American Indians. At the time the county was founded its inhabitants consisted almost entirely of New Englanders and New England transplants from upstate New York.[3] These were "Yankee" settlers, meaning they were descended from the English Puritans who settled New England during the early 1600s. They made up virtually all of Winnebego County's inhabitants during the first several decades of its history. In this regard the county was similar to most of the northern portion of the state of Illinois, and almost all of the neighboring state of Wisconsin. After the conclusion of the Black Hawk War there was an additional surge of immigration from New England. As a result of this heritage the inhabitants of Winnebego County considered themselves, and functioned as, a cultural expansion of early New England culture.[4] In the Presidential election of 1860, Abraham Lincoln won 3,985 votes in Winnebago County, whereas Steven Douglas only won 817 votes.[5]

Winnebago County for its first year of existence

Winnebago County in 1837, reduced to its current borders by the creation of Stephenson and Boone Counties

In recent years, average temperatures in the county seat of Rockford have ranged from a low of 11 °F (−12 °C) in January to a high of 83 °F (28 °C) in July, although a record low of −27 °F (−33 °C) was recorded in January 1982 and a record high of 112 °F (44 °C) was recorded in July 1936. Average monthly precipitation ranged from 1.34 inches (34 mm) in February to 4.80 inches (122 mm) in June.[7]

As of the 2010 United States Census, there were 295,266 people, 115,501 households, and 76,854 families residing in the county.[13] The population density was 575.2 inhabitants per square mile (222.1/km2). There were 125,965 housing units at an average density of 245.4 per square mile (94.7/km2).[6] The racial makeup of the county was 77.4% white, 12.2% black or African American, 2.3% Asian, 0.3% American Indian, 4.9% from other races, and 2.8% from two or more races. Those of Hispanic or Latino origin made up 10.9% of the population.[13] In terms of ancestry, 25.6% were German, 13.5% were Irish, 9.4% were American, 8.7% were Swedish, 8.3% were English, and 7.4% were Italian.[14]

Of the 115,501 households, 33.1% had children under the age of 18 living with them, 47.3% were married couples living together, 14.0% had a female householder with no husband present, 33.5% were non-families, and 27.7% of all households were made up of individuals. The average household size was 2.52 and the average family size was 3.07. The median age was 38.3 years.[13]

The median income for a household in the county was $47,198 and the median income for a family was $59,814. Males had a median income of $48,358 versus $32,103 for females. The per capita income for the county was $24,008. About 11.5% of families and 15.9% of the population were below the poverty line, including 25.0% of those under age 18 and 7.5% of those age 65 or over.[15]

Winnebago County is comprised by the following districts represented in 2015-2016 by the following individuals listed along with their political affiliation:[16]